It my sound silly, but id recommend the BASICS.
Im amazed at how many "Professionals" are masters at particular software or area's. Yet dont know about shortcuts for Cut and Copy or how to navigate files etc etc etc... As Renai pointed out, you can get locked into an area if you over specialise if your not careful.
The Main one, Problem Solving. It ties all the basic skills together.
Never underestimate the power of problem solving for IT. Problem solving could be as simple as, How to search google for an answer to a problem. Finding that bit of key information, too, finding out about a new feature in a software package and mastering it. What does this do? How can i/team best utilise this?
It literally dumbfounds me sometimes how many times i see this cripple people who might be masters at one thing, but have little understanding of much else.
So what are the Basics?
How to Use a PC
- Cut, Copy, Paste
- How to navigate the Operating system
- File Structure
- Typing Skills
- What things do what & why?
- Installing, deleting programs
- and many more
Then we can move onto more advance topics like
- Security. Why the same password is bad for everything, etc.
- Learning to code, how and why its helpful
Then moving onto
- Learning particular programs from the big vendors.
- Specialising in areas of interest.
As others have pointed out, even when specialising in a particular area, diversify, diversity, diversify. Learn something else outside your Zone. So your a graphic artist who is amazing at xyz program? cool, ive also got skills in UX design, blah blah too.